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Taping damaged cable

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  • Taping damaged cable

    I had to move an outlet in basement, the outer cover of the cable was damaged a little while removing the metal staples. The inner insulation on conductors not damaged so I taped it with electrical tape just to be on the safe side. Is this acceptable under the NEC.
    thank you in advance

  • #2
    Re: Taping damaged cable

    Well, the Official statement is "No", since suprisingly, electrical tape doesn't have insulating properties.

    Between you and us, many of us are guilty of doing the same thing. As long as the conductors aren't damaged. For me, I like to use phasing tape to cover up the occasional gaff. White tape for romex, yellow, for 12 guage, etc. It hides better.


    • #3
      Re: Taping damaged cable

      Originally posted by tailgunner View Post
      Well, the Official statement is "No", since suprisingly, electrical tape doesn't have insulating properties.

      Please cite the source of this herecy.


      • #4
        Re: Taping damaged cable

        Electrical tape doesn't have insulating value? Somebody better let 3-M know about that. Because their website is obviously filled with false advertising:

        "The choice of more professional electricians, Scotch® Super 33+ Premium Vinyl Electrical Tape is highly conformable, stretchy in all weather, resists UV, abrasion, corrosion, acids/alkalies and is flame retardant. Scotch® Vinyl Electrical Tape 35 is a professional-grade tape that comes in 9 fade-resistant colors for phase identification and cable marking. Scotch® Vinyl Electrical Tape 88 is a heavy duty, premium grade all-weather vinyl electrical insulating tape that maintains conformability for cold weather applications and is ideal for stringent environmental and mechanical thickness needs. 3M also makes economical tapes for indoor uses and for bundling and securing wires.

        3M also provides a range of tapes for special uses. 3M™ Linerless Splicing Compound 2242 is a highly conformable rubber insulating tape designed for use in splicing and terminating wires and cables rated up to 194° F (90° C). Scotch® Glass Cloth Electrical Tapes, made of woven glass cloth with thermosetting, pressure-sensitive adhesives, electrically insulate and provide mechanical protection at high temperatures."

        And from the Pressure Sensitive Tape Council:

        "What Makes a Tape an Electrical Tape?
        By John Johnston
        PSTC Technical Consultant

        What's so special about a tape that entitles it to the title 'electrical tape? First, of course, it must function as well as its industrial equivalent, in tack, adhesion, shear, tensile and so on, as needed, to perform a useful assembly function.

        Then it must have the properties required to give it electrical insulation characteristics, and that means a high insulation resistance, even under prolonged humid conditions, and a high dielectric strength, and that includes no pinholes. Every square millimeter must work and at high operating temperatures."

        Jim Don


        • #5
          Re: Taping damaged cable

          I totally agree that "electrical tape" HAS insulating properties and thanks to JimDon for his very informative post.

          But, I'm still curious as to the answer regarding the "taping" of damaged outer cover on existing wiring. While I can see that replacement should be necessary if the damage to an existing cable goes through both outer and inner insulation and thus leaves bare wire exposed, I really would like to know what are the NEC requirements for the scenario described in the lead posting.

          I have run across that exact problem in my basement... inner wires are intact with no evidence of deterioration, but the outer insulation is damaged. I was thinking of just replacing, but is that an NEC requirement? (I've got more than enough to do already!)




          • #6
            Re: Taping damaged cable

            What, no answers?

            Let me try again: What does the NEC say about taping damaged exterior jacket on existing circuit (the interior conductor sheath is NOT damaged, just the exterior jacket.)




            • #7
              Re: Taping damaged cable

              Article 110 of the NEC covers this. The way I read it, you can make repairs to the outer jacket provided that the inner conductor sheathing is undamaged and the repairs are in a dry location. The approved UL tape is used and applied at the same thickness as the damaged outer jacket. 3M makes a self sealing outer cable jacket repair tape 2234 approved for this but you can use Scotch 33 or equivilant.


              • #8
                Re: Taping damaged cable

                Originally posted by killavolt View Post
                Article 110 of the NEC covers this. The way I read it, you can make repairs to the outer jacket provided that the inner conductor sheathing is undamaged and the repairs are in a dry location. The approved UL tape is used and applied at the same thickness as the damaged outer jacket. 3M makes a self sealing outer cable jacket repair tape 2234 approved for this but you can use Scotch 33 or equivilant.
                Could you give me the exact article? I can't seem to find anything about this in the 05 or 08 edition's of the NEC.


                • #9
                  Re: Taping damaged cable

                  I just covered the 05 NEC and didn't find anything about it.
                  info for all: --- "I like long walks, especially when they are taken by people who annoy me."


                  • #10
                    Re: Taping damaged cable

                    Correction: Somehow I got the impression this thread was about damaged jackets on extension cords, but going back and re-reading I see it is not. I will leave the information I found on extension cord use here for reference, but it of course does not apply to permanent building wiring.

                    Here is a interpertation letter that OSHA put out on this very subject:

                    Standard Interpretations
                    12/16/1998 - Using electrical tape to repair minor damage to the outer jacket of an extension cord.

                    • Standard Number:1926.403(a); 1926.403(e); 1926.405(g)(2)(iii); 1926.416(e)(1)

                    OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at

                    December 16, 1998

                    Mr. Dennis Vance
                    Safety Specialist
                    711 Low Gap Road
                    Princeton, WV 24740

                    Re: 1926.403(e); 1926.405(g)(2)(iii); 1926.416(e)(1).

                    Dear Mr. Vance:

                    This is in response to your letter of March 20, and your follow-up letter of October 9, concerning the use of electrical tape to repair minor damage (abrasions and cuts of limited depth) on the outer jacket of an extension cord. We apologize for the lateness of this reply.

                    Generally, electrical tape may be used to cover superficial damage to cord jackets

                    You ask whether there is any prohibition against putting electrical tape over these kinds of abrasions and nicks when there is no damage beyond the jacket — the conductors have not been scraped or exposed and the insulation inside the jacket has not been displaced or compressed.

                    Section 1926.416(e)(1) provides that "worn or frayed electrical cords or cables shall not be used." Superficial nicks or abrasions — those that only slightly penetrate the outer jacket of a flexible cord, and do not permit the cord to bend more in that area than in the rest of the cord — do not normally render a cord "worn or frayed." Therefore, there is no need to repair or replace such a cord.

                    Recommendation against taping

                    While taping these incidental abrasions and cuts does not necessarily violate any OSHA standard, we recommend that employers not tape this type of damage for two reasons. First, Section 1926.403(a) requires that "all electrical conductors and equipment shall be approved." This standard precludes the use of approved electrical conductors and equipment if their characteristics are significantly altered. Applying electrical tape that is too thick or applying too much of it could change the cord's original flexibility and lead to internal damage. Second, the depth of the abrasions and cuts cannot be monitored to see if they get worse without removing the tape.

                    It should also be kept in mind that the heavy-duty extension cords commonly used on construction sites are designed to withstand a hostile environment. Damage to an extension cord that is bad enough to consider taping may have caused damage beyond the jacket.

                    Tape may not be used to repair significant damage to cord jackets

                    Repair or replacement of a flexible cord (depending on its gauge) is required when the outer jacket is deeply penetrated (enough to cause that part of the cord to bend more than the undamaged part) or penetrated completely, or when the conductors or their insulation inside are damaged. Two provisions of the standard prohibit the repair of the jacket of a worn or frayed flexible cord with electrical tape. Section 1926.403(a) requires that the cord be approved. The original approval of the cord was based on the types of materials and construction used. As noted above, taping the cord can change the flexibility characteristics of the cord, which in turn can affect the amount of stress in the adjacent areas. This is of particular concern with respect to the grounding wire. Also, the jacket is designed both to prevent damage to the conductors and insulators inside and to further insulate the conductors. Taped repairs usually will not duplicate the cord's original characteristics; in most cases neither the jacket's strength nor flexibility characteristics will be restored. Therefore, tape repairs of the jacket may not be used to bring a worn or frayed flexible cord into compliance.

                    In addition, Section 1926.405(g)(2)(iii) states that "flexible cords shall be used only in continuous lengths without splice or tap. Hard service flexible cords No. 12 or larger may be repaired if spliced so that the splice retains the insulation, outer sheath properties, and usage characteristics of the cord being spliced." This standard precludes the repair of flexible cords smaller than No. 12.

                    MSHA has a different standard governing the repair of flexible cords

                    You point out in your letter that U.S. Department of Labor's Mine Safety and Health Administration (MSHA) permits the taping of damaged flexible cords in mines, which are, in many cases, very hazardous environments. The standard that applies in mines is different from the OSHA standard. The MSHA standard, located in volume 30 of the Code of Federal Regulations, Section 75.517, provides that "power wires and cables...shall be insulated adequately and fully protected."

                    A mine employer complies with this standard by "insulating adequately and fully protect[ing]" the cord. By its terms, this permits the use of cords as long as they are properly insulated and protected. Where that can be accomplished by the proper application of suitable electrical tape, the requirements of that standard are met. In contrast, the OSHA standard, which is based in large part on the National Electric Code, requires that the cords be "approved," and prohibits the repair of cords smaller than No. 12. Consequently, the use of tape to repair a worn or frayed cord is permitted under the MSHA standard but not under the OSHA standard.

                    if you require any further assistance, please do not hesitate to contact us [by fax at: U.S. Department of Labor, OSHA, Directorate of Construction, Office of Construction Standards and Guidance, fax # 202-693-1689. You can also contact us by mail at the above office, Room N3468, 200 Constitution Avenue, N.W., Washington, D.C. 20210, although there will be a delay in our receiving correspondence by mail.]


                    Russell B. Swanson, Director

                    [Corrected 6/22/2007]
                    Last edited by Bob D.; 06-11-2009, 04:34 AM.
                    "It's a table saw, do you know where your fingers are?" Bob D. 2006



                    1/20/2017 - The Beginning of a new Error


                    • #11
                      Re: Taping damaged cable

                      This falls under "the discretion of the local inspecting authority". The inspector can argue that the cable is no longer approved since the jacket is torn and no longer is truly an NM-B (I assume that's what your using) type. Regardless whether or not the interior conductors are damaged the integrity has been compromised. An installer would argue that the internal wire is fine and since a junction is not needed it can be taped and does not need to be in a box. The inspector can then say it's not a UL listed repair, screw you rip it out. Or go get said repair UL listed. Same thing. So at the end of the day most inspectors see this happen and can tell by feel if it's minor or major. If it's minor they let it slide if the rest of the work looks well executed. It's also a good reason to be nice to the inspector.